Disposal process for the treatment of weak ammoniacal waste liquors from coal distilation plants



Feb. 6, 1940. w. o. RENKIN 2,189,083

DISPOSAL PROCESS FOR THE TREATMENT 0F WEAK AMMONIACAL WASTE L'IQUORS FROM COAL DISTILLATION PLANTS Filed oct. 2:5, 19s? 2 sheets-sneer 1 Feb. 6, 1940. w. o. RENKIN 2,189,083

DISPOSAL' PRocEss FOR THE TREATMENT oF wEAK AMMONIACAL wAsTE LIQUoRs FROM COAL DIsTILLATIoN PLANTS Filed Oct. 23I 1937 I 2 Sheets-Sheet '2 Patented Feb. 6, 1940 DISPOSAL ,PROCESS FOR THE TRATMNT O F WEAK AMMONIACAL WASTE LIQUOBS FROM COAL DISTILLATION PLAN '.lSA

William 0. Renkin, New York, N. Y., assigner to Lancasterliron Works, Inc., Lancaster, Pa., a

corporation of Pennsylvania Application October 23 les?, serial No, `170,573

' s claims. (o1. ca -100,)

, My present invention -relates to methods and apparatus for the purification or clarification of the noxious Waste liquors which result from the operation of by-product coke oven plants and to the manufacture of commercial ammonium chloride powders from such liquors;

In the operation of by-product coke oven plants, the liquid *coming from ythe cooling gas mains, etc.,.commonly called gasliquor or ammonia 1iquor?.. ispassed through a free ammonia tower where the greater part of the free ammonia is distilled roff and passed on to a sulphuretor pro,- ducing ammonium sulphate. Whenthe phenolic content of the liquor effluent from the free ammonia lstill is sumcient tomake phenol` recovery practical .or necessary, the 'elu'ent is passed to a dephenolization towerwhere the greater part of thephenol is recovered and discharged as sodium phenolate, the phenol removal being generallyfrom 95% to 98% ofhthe'original phenol content. The liquid passing from the dephenolization tower constitutes a noxious waste called Weak ammoniay liquor*y containing ammonia, chlorine, sulphur, phenol, tar, coal dust, coke dust, and4 otherimpurities, 'and this weak ammonia liquor has' given rise to nuisances so serious as to threaten the legal operation lof the coal distillation plants. It has '.beenythe common practice' to pass this weak ammonia liquor through an additional or fixed ammonia still where lime is added, f changing the ammonia chloride base solution to a calcium chloride base to enable the liquor. to be commercially handled. This lime treatment, whileflxing a substantial part of the ammonia, results in a waste liquor, commonly called still'waste, which contains all of 'the above substances and calcium salts in addition. Because of its offensive character, this still-{waste cannot .be discharged intostreams, ponds-or sewers and it has `therefore been usual to mix the still waste liquor with the water used to quench the. hot coke removed from the coking ovens, thereby disposing of it. By this vpractice the still wastes are converted intos'team and' other dusty, acidladen Vaporswhich remain an unso far as I am aware, efforts by othersv to effect their clarication have failed,rdue, `in -my opinion to the assumption made by other investigators that someofthe various substances c ontainedin` the waste liquors' were present in the formfofv fluid compounds. vSuch efforts as have been made have therefore proceeded on the theory that chemical ltreatment; for separation was necessary and, as there are approximately ninety known diierent substances containedin the waste 'liquors all proposed procedures .for removing; v

them chemically have proved impractical andun` successful.

AWhere my present process ispracticed, nolime'flo is added to thel liquor, thereby saving the cost of the lime, and the usual fixed ammonia Ystill l may be employed as a second free ammonia still x to recover a further quantity of free ammonia.

The etlluent then resulting is a weak, vimpurel I have discovered that no ap-'-y ammonia liquor. preciable quantities of known'ujid compounds, othervthan phenol, are contained inzthis liquor, but that all of the other impurities. exist therein as solids in mechanical suspension and salts in aqueous solution, capable of removal by mechanyical means.` However, my extensiver investiga- Vand apparatus for mechanically extracting the solids from the liquor, at the same time separ- "ating the tar and'dirt from vthe ammonia salts, 1,.,

`the vliquor being kept in constant agitation to prevent agglomration of the tarry insoluble particles. f f Accordingly, the principal objectof my vvpresent invention maybe saidto consist in providing a I 'method andapparatus for leconomically separating the solids from the weak ammonial liquorsp thereby purifying the liquors and at the same ,time segregating the solids to recover a dry` and lcommercially valuable ammonium chloride powder. Other and furthenob'jectsrwill appear from the following specification.

Referring yto thev drawings which forma part of this specification:

Figure 1 is a schematic illustration of apparatus in combination for carrying out my improved process. i

`Figure 2 isa similar illustration showing va 'somewhat different arrangement of apparatus forv 'practicing a modication of my improved process,

and

Figure 3 illustrates .on

a larger scale and-infl greater detail the interconnected flash type stills yshown in Figurel.

As above stated, ,I .have `deterrrlined 'thattlie 5 5 solids in the weak ammonia liquor are composedl partly of inorganic matter in true aqueous solution and partly organic matter in mechanical suspension, the matter in suspension being so iinely divided asi to be` imperceptible and the liquor appearing to be clear. This liquor differs in different plants and at different times in the operation of a particular plant, but in general its composition can be taken approximately as follows:

Inorganic solids in aqueous solution.:

Grams vper litre Ammonium chloride NI-IiCl 9.9'3

Tarry matter y .7`9

Acetates and salts of other fatty acidsv .04

Catechol and-homologues ."02 Coal, coke dust, and other impurities; .l

Ammonium sulpho-cyanate NH4SCN .58

Ammonium thio-sulphate (NH4)2S2O3 .53 v

Ammonium sulphate 29 Terai sonas in S01un0n 11.33

Organic solids in mechanical suspension:

f i Grams per litre Sulphur Briefly, my process for purifying thisv liquor therefrom is as follows: The liquor is rst treated to obtain a concentrated liquor, in which the in-` solubles appear in a flaky, nodular or granular form. This vconcentratedaqueous liquor is lkept 'in a state of agitation to prevent the insolubles frornsettlingy out or agglomerating and the liquor is then ltered to remove the insolubles in a conditionv permitting them tol be easily handledand stored or burned with other solid fuel. Thereafter thev salts remaining in solution are dried by removing the remainirug.moistures from the ltrate. As` the concentrated 4solution is highlycorrosive and difcult'to handle, thisis preferablyaccomplished by spraying the filtrate in a flash drier or other similar desiccating ap- 'paratus ,designedI to suddenly snap oil the water. Thus treated, the salts are precipitated as a commercially valuable -brown powder, the value of which may bevincreasedby adding a decolorant,

such as activated carbon to thekltrate. and refiltering before drying the salts;y or all or part of the powder may be redissolved, decolorantadded, and the resulting solution ltered and passed to the desiccating apparatus. Due tothe corrosive character .of the liquor, concentration above twenty per cent-shouldbe avoided, and due to the normal tarry character ofthe solids in suspension, care must be taken to ymaintain the 'liquor inA constant agitation to prevent aggiorn'- eration of the insolubles. Yet, since agitation at excessive speed or high temperatures render the corrosive eects of eveny weak ammonia liquor great, caremust also bel exercised to avoid un,- duly high temperatures or too violent agitation. When the phenolic content of the weak ammonia .liquor is sucient to ybe objectionable, I first treat `the liquor with a deodorant, such as Nuchar,

or other activated carbon, having an affinity for the phenol, the deodorant being added in volume Vapproximately equal to the phenolic content or sufficient to neutralize and adsorb the phenol and hold itin the liquor during the next succeeding steps of the process, such deodorant being -ultisubjecting it to the effects of a plurality of interconnected flash type stills 2,0, 33,1143 Vvand 59, the `latter of which is heated by steam or other fluid heat mediuml supplied through thefpipet;

To avoid repetition, like parts of the several stills are indicated by reference characters having the same units gures, the several stills being. substantially identical vin construction. Thus, the still Eil consists of aplurality of vertical tubes 5I fed at their lower ends by the liquor supply s pipe 47' and opening into an enclosed head chamber 52 under a dome-shaped baiile lplate 53.`

Inoperatiom thehotsteam circulating between the tubes of still V5.0 vapor'izes water fromthe liquor in the tubes, thevlighter portions of the:

vapor rising around the baille, throughsc'reen y54, and out in the form of a finely4 divided mist. Portions of the rising vapor too heavy to pass through the screen are dropped Abaci: onto ,thel

baille by which they are directedinto the trough 56. The warm misty vapor passing the lscreen `is utilized to heattheencased tubes lof 4the similar still 46 to 'Whichlit isconducted bythe pipev 55,

said vapors being .condensed and drained as wai,

ter into-thesurnpv athroughvpipe 48. The va-` porsv ilashed-r from Ythe liquor of still which are suiiciently light to pass as mistl through` screen 44, in turn,l 'are conducted'through pipe to heat still 351m which such vapors are condensed and drained as' Water into the `common Similarly vapors passing 45 sump through pipe 38; from still 30 are conducted to still 20, condensed and drained as clean water to the sump,` while vapors rising from the liquor inl the tubes of still v 20 and passing as mist through its' screen rise through pipe 25-to a condenser 65.

In the course of theirconcentration, the waste liquors pass in a substantially reverse direction,

`counterilow to thefheat exchange, being firstV admitted through pipe iB to the tubes of still-2i] in which'the distilled vportions too heavy to pass the screen 24 are precipitated and collected in trough 26 and are led'therefrom through pipe 2 1 to the tubes of still 3U. The further concentratedliquor collected in trough 36is led through -pipe 31 to the tubesof still 49 and there further distilled, while the concentrate ,dropping from the screen 44 isdirected by, baie 43 into trough 46 and leditherefrom to'fthe: tubes of still 5i) through pipe 41. l' i y In this manner, the Waste liquors may be very eiiciently and economically concentrated, the stills operating on the vapor-phase and theunit of lowest concentration '20, being" under a vacuum created by the condenser, requires the least heat for operation. ""ihe intermediatenits, B and 40, operate under progressively lesser degrees of vacuum .and ytherefore require proportionately more heat, while the unit of highest concentration 5B ismaintained at a neutral or plus pressure at'theEheat source.

J Othermethods and'rmeans 'may be devised for agentI such as activatedcarbon. is added. from Obtaining?'the-9011Cei1iwtedx.;lqiolfbut I .here found.: that; certain 'conditions must Aloe I metfr if.

the-valuable ammonia salts areto be economi-y cally extracted and these conditions are satised ,by ,the utilization oiimore than two i'nQtkroonnectj4 ed iiashg type stills las above described, For lin-k l stance it is necessary to ykeep,y the-soluble'inorganicsolids in solution rand togholdftlufe'tarry organic solidsin suspension so thatftliey'lwill not agglomerate and settle'outLc It is'l therefore necessary to keep `the liquor in facon'stanustate of agitation as otherwise 'the yorganicsolidswill agglomerate andas. thel liquor approaches the required concentration, the's'olublesmwill lbe pre.- l cipitated. On themultipleeilect fiashjtypestiils i preferably employ, the liquor is kept in constant agitation, yactually travelling up through the sep-I aratestills at a speed of morefthan vtwenty feet Per. Segond (buflss than Sixty feet Der. gewild! as abovethisspeed erosion of thevstillsoccurs) bringing the. volume'. down to approximately seven and onehalf percent of the originalweal; ammonia liquor volume. .At this concentration the'insolubles .and organic substances, *succhi` as tanI catechols, homologues,y inecoal and, vcoke dust,` separateinto flaky',` nodular;` or granular form. l This 'separation of the insolubles appar-y ently occurs betw'e'ennine-f'and six'fper Acentfof the original volume,` or, differently statedgwhen the liquor is concentrated tota 4solid''cohteifit between' twenty and thirteen per4 cent. Itjwill be -found that the insolubles willf be'ginjtofappear iny this peculiar condition Wliienftl'iev liquor yreaches a vconcentration of about ten per cent of its original volume. At a concentrationv ofveper cent j of the original volume it is impracticable by agitation to lprevent'the insolubles fromagglomerating into a pasty mass. The inorganic and soluble substances having beenl prevented from individual separation .during thel .concentration of the liquor'` remain in solution. v

" The concentrated liquor discharged from the stills through 4pipe 51.is permitted to cool toroo-m temperature (less than o deggrahro, at the same time being slowly agitated to keep the in-` l solubles from`settling.out. v As thetim'e required 'for this cooling is short, it ymay be conveniently `effected in asurge tank 1l)` having approximately one hourc'apacit'y, theliquor being fed into the tank adjacent itsb'ottom at one endvand flowing out through a pipe 1l at the other end of the tank` adjacentits'top, a screw 12 operating'to maintain the required agitation.

' The insolubles are then'removed'fromthe liquor in av suitable tar extractor or, more preferably,

.ina rotary-type'vacuum filter where thetar and other 'insolubles are practically all removed in anon-nasty formation capable of being handled,y

`stored or readily fedinto a furnace with other solid kfuel. .14 indicates a rotary type vacuum iilter intothe trough of` which the cooled concentrate is fed at proper speed through the pipe 1|. "The liquor carrying the inorganic matter in solutlonis drawn by'vaouum into the revolving drum 16 through its porous cylindricalwalls" and discharged from thendrum adjacent its hub while the insoluble and organic solids are filtered out i andadhere to" the` surface of .the drum fromwhich they are scraped ,by a blade 11 into. a chute 18 by which, they are.A discharged into a suitable 'I'he filtered liquor, 'now practically free of tars and other insolubles, is pumped through a pipe 19 into a mixing troughvor surge tank 85, similar to the. twill Where an inhieiwir 0r memorizing.,

a supply` at 98'1and thoroughly lmixed withthe solution. The l'liquor tlms treated is thenl fed through pipe 81 toa continuous rotary type vacuum filter 88, ,similar to the filter 15, wherethe decolorizing agent is removed to be deposited,

if ldesired, into the receptacle 8i) along with the tar and insolubles removed inthe first filtering n operation.

The remaining water is `thensnapped oi .to precipitatethe soluble solids asa dry,`marketable,y ammonium chloride powder useful instorage bat# teries, for galvanizing and tinning processes, etc.

The remaining water may be removed in a flash dryer orr desiccating retort 90 which comprises a chamber of brick o-r concrete intolwhich the concentrated solution is atomized or sprayed as a ne mist through a nozzle 9|. Airor other dry gas, suitably heated by a burner92, is introduced intothe chamberthrough a" duct 93 and drawn vout by fan' M through a dustcollector 95'. In e mingling with the hot currentl'of gas, the remaining moistures `are driven from'the solution and the solids are thrown down inthe form of a dry powder at the bottom of the retortand may be removed therefrom through the gate 95.

The composition of this dry powder von a dry basis is approximatelyas followsz/ When a more'rei'lned product, or one having ai lower percentage of impuriteaisrequired, all or a portion. of the powder may be re-.dissolved by mixing with water from a water supply 86 to form approximately a ten per cent concentrated solution and this ,solution either again treated with a decolorizing agent and iiltered, or ltered without adding any decolorizing material. This may be done b-y positioning the gate 96 to dis# v chargethe powder;l or some portionV of it, ,from-y the desiccating retort 90 into aconduit 8l whichdelivers the powder back to the mixing trough' or surge tank Awhere water ifor re-dissolving the being also added from source `v98 when desired.' The solution then proceeds through the iilter 88 and back tothe desiccating retort where the further 'rened ammonium salts'are again dried and thro-wnvdown. y

f, powder is added` from afsource "86, `decolorant I have found that by redi'ssolving, r'e-iltering and re-dryingl the powder inthis manner,`thef` size of the particles orcrystalscanvalsof `be in-` creased, thus adding to the'valuecf theprod-f' uct. At the same time, anyjvery fine tarry par;l ticles not removed in the initial iiltering operation grow injdimension'and may be completelyl ltered out whenfpassed tov the iilter the sec-.2

ond time. y. q. y 4

My process may be simplified` where -heat isv cheaply available by immediately snappingoiy all the water from thev weak ammonia" liquor,` instead of passing' it throughzthe flask stills shown in Figs. landfthereby. precipitatingfall'fthe solidsQboth soluble 'andinsolubla vas 'a powder, and then mixing the pc'iwderwithv water t'ofiorin' a concentrated liquor containing about` terrper l and 3, and in which'lQQ indicates a flash dryer or desiccating retort similar to the dryer 90; a mixing box or surge tank similar to the tank 85 isv indicated at HB5, anda tar lter similar' to the filter tti is indicated at E86, all 'comparable parts of the modied'apparatus'being' designated by the same reference gures with the addition of 100 to avoid repetition. Here, the weak ammonia liquor is fed directl tothe atomizer iti ofV the drying retort through' lsupply pipe l it and dry air or c-ther gas, suitably heated by burner 92, is introduced into the retort through a ductl lg@ anddrawn out through ay dust collector lg to va stack. In mingling with the hotgas current, all water is driven oi, and

the solids, both soluble and insoluble, are precipitated or thrown down as powder atthe bottom of the retort lfrom which thev powder is discharged through gate tt into a conduit I9? and carried to the surge tank 35, there lto be mixed with water from a source 58e to provide a liquor, of not more than twenty `per cent concentration. If desired, decolorant may be addedito the` mixture from a source |98: The mixture is constantly agitated in the mixing box |85 for from twenty 'to sixty minutes to thoroughly dissolve the valuable soluble sal-ts, to prevent agglomeration of the insolubles and to properly mix in any decolorant. The concentrated liquor thus obtained then flows from theA surge tank to ythe tar filter .9&8 Where all the undissolved solids in suspension, including any decolorant are removed, the

ltrate being pumped vto the desiccating vretort where the water is snapped ,oil to throw down a refined and commercially valuable ammonium itv chloride salt,

Where a more-highly rened product is required, the ammonium chloride powder may be again. dissolved, treated and dried, the size of the crystals increasing with veach filtering and the 'powderbecoming cleaner and whiterwith repeated treatments of ythe decolorizng agent. l

On the other hand, wherev a highly reiined product is unnecessary, as for usual commercial purposes,-the apparatus may be continuously op-` erated after the rst hour by adjusting the gate |96 to return only a portion of the powder to the surge tank H35, permitting the balance to.

run oi as nished product. For illustration, if

the gate is adjusted to discharge one -half the l powder and to deliver the other, half into the conduit |91, eventually one half of the product will be at least twice refined and ltered, one quarter Will be ltered three times, one eighth will have been redissolved and reiiltered four ftimes',v etc., etc., the more highlylrerlned white crystals mixing with the smallerand darker crystals .to obtain a product of satisfactory quality.

What I claim and desire to secure by'vLetters Patent is: y

1. A disposal process for the treatment of weak ammoniacal waste liquors from'coal 'distillation plants, containing tar, insoluble solids', soluble salts and other impurities and in which the major portion of the ammonia is presentk as, ammonium chloride, which comprises the stepsY of evaporate ingy said weak ammoniacal waste liquors thereby producing a concentratedliduor containingall' Y the tars, insoluble vsolids and impurities of ythe original 'liquor ata strength wl/iereithe insolubles separate, andcontinuously agitating the liquor' during the concentration'step to prevent ySegre-ff gation andprecipitation of the tars and insoluble solids, filtering the concentrate rto removetars' and yinsoluble solids, flashing the `moisturecone-` tained therein by vspraying the ynitrate intona stream of heated gaseous material to precipitate.

the soluble salts as a dry powder, consisting large# ly oframmonium chloride. i

2. A disposei process for the treatment er weak.

ammoniacaly waste vliquors from coal distillation plants, containing tar, insoluble solids, 'soluble salts and other impurities and in which the major portionfof the ammonia is present as ammonium*` .1 chloride, which comprises the steps of addiri`g an,

activated carbon "and of. evaporating said weak` ammoniacal waste liquorsV thereby producingja; concentrated liquor containingrall of the tars and insolublesolids of the original liquor at a strength where the insolubles separate, and continuouslyvi agitating the liquor during .l the concentration thereof to prevent segregation and precipitation1` of the impurities, filtering the concentratetore-1l move tars and insoluble solids, including the actii 1 vated carbon, to be subsequentlyfburned, adding' activated carbon Ato the `nitrate, reltering the ,30. the nitrate by" spraying the nitrate inte 'a stream of gaseous material to precipitate'the solublesalts as dry powder, consisting largely of ammoniumL ltrate, `and flashing the moisture `contained in chloride. i f i 3. A disposal process A`for theA treatment n of weak ammoniacal 'waste liquors from coal dist lation plants, vcontaining tar, insoluble solids, soluble salts and othery impurities and inlwhich the major portion of the ammonia is present asl am: monium chloride, which comprises the steps of evaporating weak ammoniacal waste liquors thereby producing aconcentrated liquor 4containing ali of the impurities ef the originar liquor; 4' i a strength whereftheinsolubles separate, ragitating the liquor during the concentration thereof to prevent'segregation and precipitation of fthe,r` i

impurities, ,filtering the. concentrate to remove tars" and insoluiiley solids, iiashingjthe vrnjoisi'luref' contained therein by spraying the iiltrate intolaj Y stream of heated gaseous materialto precipitate the soluble salts as a dry powder, consisting largely of ammonium chloride, andimproving the. kduality 'of said kdry powder' by' dissolvingfthedry y powder in water to forma concentrated solution, adding activated carbon, iltering the concentrate to remove theactivated carbonl and certain purities adsorbed therein, and again flashing the moisture containedv in the iiltrate by spraying i'tj into a stream of heatedgaseous material to piers cipitate the soluble salts as dry powder,y consis ing largely of ammonium chloride, in a more re-r-v fined condition.

4. A disposal process'fol th'e treatment ofweak ammoniacal waste liquors from coal 'distillation' plants, containing tar,`insoluble solids, soluble v salts and other impurities andl in which the major portion of theammonia is present as ammonium chloride, which consists I passing the liquor through a Aseries of flash stills at a highspeed to concentrate it and simultaneously to'continuthe concentrate to remove tar and insolublesolids,` and flashing the moisture contained,v in the "I0 f` ously agitate it to prevent SegregationandI prei cipitation of the tars and insoluble solids', filtering.y v

filtrate vtoirecover clean' water" and 'water vapor; 75: I

by spraying it into a stream-of heated gaseous material and precipitating the soluble saltsas dry powder, consisting largely of ammonium f chloride.

5. A disposal process for the treatment of weak ammoniacal waste liquors from coal distillation said liquors by spraying it into a stream of heated gaseous material, andv depositing all tars, insoluble solids and soluble salts, adding water to said residue to produce a concentrated liquor, and

continuously agitating said liquor to prevent seg-- regation and precipitation of the tars and insoluble solids, filtering the concentrate to remove'tars and insolublev solids, and flashing the moisture contained in said concentrate by spraying it into a streamof heated gaseous material to deposit the soluble salts as dry powdenconsisting largely of ammonium chloride.

6. A disposal process for thetreatment of weakY ammoniaca] waste liquors from coal distillation plants, vcontaining tar, insoluble solids, soluble salts andother impurities andin which the maj or portion of the ammonia is present as ammonium chloride, which consists in passing the liquor through a series of flash stills to concentrate it and at a suiiciently high speed to prevent segregation andprecipitation of the tars and insoluble solids, ltering the concentrate to remove tar and insoluble solids, and flashing the moisture in the filtrate by spraying it into a stream of heated gaseous material -to remove the moisture in the form of clean water .and water vapor and to precipitate the soluble salts as dry powder, consisting largely ,of` ammoniumchloride, dissolving the dry powder'to form a concentrated solution, adding activated carbon, filtering the concentrate to remove the activated carbon and certain impurities adsorbed therein, and' again flashing the moisture in the filtrate to precipitate the soluble salts as dry powder, consisting largely of am* monium chloride of improved quality, and in-` plants, containing tar, insoluble solids, soluble salts and other impurities and in which the majo-r portion of the ammonia 'is present as ammonium chloride, kwhich comprises the steps of evaporating said weak ammoniacal waste liquors producing a concentrated liquor containing all of the tars and insoluble solids of the original liquor, continuously agitating the concentrate to prevent the segregation and precipitation of the impurities, ltering the concentrate to remove tars and insoluble solids, flashing the remaining moisture to separate clean water and water'vapor by spraying the ltrate into astream of heated gaseous material to precipitate the soluble salts as a dry powder, continuously withdrawing portions of` said powder as a riished product, continuously withdrawing other portions ofv said powder for further treatment, and adding water to the latter portions of said powder to form a concentrated solution, adding activated carbon to said solution, :iiltering out said activated carbon and its adsorbed impurities, and again flashing `moisture contained in lthe ltrate .and recovering clean vwater, and precipitating the soluble salts as dry pow-der, consisting largely of ammonium chloride with the soluble salts precipitated from the orig-l inal liquor, to improve the quality of the finished e product.

8. A disposal process for the treatment of Weak ammcniacal waste liquors from coal distillationy plants, containing tar and insoluble solids oi such character yas to preclude their separating by settling, and including soluble salts and other impurities and in which the major portion of thev ammonia is present as ammonium chloride, which comprises the steps of distilling off aqueous portions of the liquor to concentrate it to less than 10% of its original volume while-keeping the liquor continuously agitated to prevent segregation and precipitation as the liquor becomes concentratedltering the vconcentrated. liquor to remove tars and insoluble solids, and flashing the moisture in the iiltrate to separate clean water and water vapor and precipitating the soluble salts as a dry powder, consisting largely of ammonium chloride.

" WILLIAM O. RENKIN. 

